In the normal central nervous system (CNS) the intact blood-brain barrier (BBB) plays a protective role, restricting the movement of potentially damaging agents into the brain or spinal cord. This barrier, however, also prevents therapeutic substances from interacting with the CNS. Selective, reversible disruption of the BBB may permit the delivery of therapeutic agents to the CNS. Using high intensity focused ultrasound (HIFU), we have developed a novel method for selectively disrupting the BBB in a reversible, controlled manner. In particular we can selectively target and disrupt the BBB in a particular region of interest (RO1) as small as 1 mm3 in volume that permits flux of a molecular complex 69,500 Daltons in size. Based on this work, we propose further studies on the effect of HIFU on the BBB. These studies include determining the mechanisms of HIFU's effects on the BBB, documenting the duration of BBB disruption, and clarifying which molecules can pass through the disrupted BBB. We believe that HIFU represents a powerful therapeutic tool in the treatment of a variety of CNS diseases.